In a liquid crystal display device, a thin-film EL (electroluminescence) display device, an organic EL display device or the like, an amorphous silicon film has been conventionally mainly used as a semiconductor film that functions as a channel layer of a TFT (thin-film transistor) which is a semiconductor device.
In recent years, however, attention has been focused on an oxide semiconductor film mainly composed of an In—Ga—Zn-based composite oxide (hereinafter also referred to as “IGZO”) as the aforementioned semiconductor film, because of the advantage of higher carrier mobility as compared with the amorphous silicon film.
For example, Japanese Patent Laying-Open No. 2008-199005 (PTD 1) discloses that this oxide semiconductor film mainly composed of IGZO is formed by a sputtering method by using an oxide sintered body as a target.
In addition, Japanese Patent Laying-Open No. 2008-192721 (PTD 2) discloses that a channel layer is formed by a sputtering method by using a target including titanium or tungsten and indium, and thus, a TFT having excellent operating characteristics is obtained.
In addition, as a material suitably used when forming an oxide transparent electroconductive film by a vacuum vapor deposition method such as an electron beam vapor deposition method, an ion plating method and a high-density plasma-assisted vapor deposition method, Japanese Patent Laying-Open No. 2006-347807 (PTD 3) discloses an oxide sintered body including indium oxide having tungsten solid-dissolved therein, including tungsten with a ratio of atomic number of tungsten to indium being equal to or higher than 0.001 and equal to or lower than 0.034, and having a density (apparent density) of equal to or higher than 4.0 g/cm3 and equal to or lower than 6.5 g/cm3.